1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly to a method for reporting channel quality information in a wireless communication system.
2. Discussion of the Related Art
In order to effectively implement communication between a transmission end and a reception end, the transmission end must feed back channel information to the reception end. In general, downlink channel information is transmitted from a user equipment (UE) to a base station via an uplink, and uplink channel information is transmitted from a base station to a UE via a downlink. The above-mentioned channel information is referred to as a channel quality indicator (CQI). The CQI can be generated in various ways.
FIG. 1 is a conceptual diagram illustrating generation and transmission of a channel quality indicator (CQI).
Referring to FIG. 1, a UE measures a downlink channel quality, and reports a channel quality indicator (CQI) value based on the measured downlink channel quality to a base station via a control channel. The base station performs downlink scheduling (UE selection, resource allocation or the like) according to the reported CQI.
In other words, when a base station allocates radio resources to a UE in a wireless communication system, the base station uses a CQI received from the UE.
The UE receives a pilot channel or the like from the base station, measures channel quality information such as a Signal to Interference Ratio (SIR) or the like about the received signal, and reports the measured channel quality information to the base station. The base station allocates radio resources to each base station using the channel quality information received from each UE.
The UE may periodically or aperiodically report channel quality information to the base station.
In addition, the UE may report channel quality information to the base station via a Physical Uplink Control CHannel (PUCCH) or a Physical Uplink Shared CHannel (PUSCH). The PUCCH and the PUSCH use different coding methods, wherein the PUCCH has high decoding performance superior to that of the PUSCH.
If there is a need for a UE to transmit a larger amount of control information than that capable of being transmitted via a physical uplink control channel (PUCCH), or if a UE desires to improve transmission performance of control information, the UE transmits channel quality information to the base station via a physical uplink shared channel (PUSCU).
In accordance with the related art, a UE can transmit channel quality information to a base station via a physical uplink shared channel (PUSCH) only when receiving a permission message from the base station.
A Long Term Evolution (LTE) system can support a system bandwidth from 1.25 MHz to a maximum of 20 MHz. Therefore, a method for transmitting channel quality information according to the related art has described a method for transmitting channel quality information of a 20 MHz—bandwidth.
However, a LTE-A system collects five 20 MHz bandwidths through carrier aggregation, and thus supports a 100 MHz bandwidth. Therefore, there is needed a method for transmitting channel quality information about the 100 MHz bandwidth.